1. Field of the Invention
The present invention relates to a passive optical network (PON), and more particularly, to a method and system for determining and controlling output power of an optical transmitter of an optical network unit (ONU) in a time and wavelength division multiplexing passive optical network (TWDM-PON).
2. Discussion of Related Art
With the development of optical communication technologies and a rapid increase in the demand on Internet services, fundamental researches on optical network have been conducted since the early 2000s. As a result, broadband networks, such as Fiber To The Home (FTTH) and Fiber To The Office (FTTO), have emerged and become common, in which the broadband network directly connects a base station or a central office (CO) to a subscriber using optical fibers.
In addition, numerous researches have been recently conducted on technologies of the next generation high-speed and high-capacity optical network to cope with an explosive increase in traffic according to proliferation of mobile IP terminals, such as a smart phone or a table computer, commercialization of IPTV services, and proliferation of multimedia broadcasting/streaming services over the Internet.
As a method of effectively providing services to more subscribers based on limited network resources, a Time Division Multiplexing (TDM) method and a Wavelength Division Multiplexing (WDM) method have been applied to the optical network technology. In addition, many researches have been conducted on an optical network using a hybrid method to which the TDM method and the WDM method are applied together.
Among them, by using a time and wavelength division multiplexing (TWDM) optical network technology belonging to the hybrid method to which the TDM method and the WDM method are applied together, a consistent demand on extension of a network bandwidth may be satisfied, and a communication capacity and the number of subscribers may be easily increased while a high-speed communication service is provided to a large number of subscribers. Accordingly, a great amount of researches have been conducted on the TWDM optical network technology serving as a candidate for the next generation optical network following the 10G-passive optical network technology.
Meanwhile, according to the International Telecommunication Union Telecommunication Standardization sector (ITU-T) for standardization of optical networks, a TWDM PON technology and a point-to-point WDM technology are selected as primary technologies of the NG-PON2 (40-Gigabit-capable passive optical networks), and standardization thereof is in progress.